How to rbind multiple matrices into one big matrix

Question

I defined a function to process each csv file and it returns a matrix. I would like to use this function in a for loop to process all the files and combine all the data into one big matrix. But it seems this code does not work.

filenames=dir()

bigMatrix = processEachCSV(filenames[1])

for (i in 2:length(filenames1)) {
  x = processEachCSV(filenames[i])
  bigMatrix=rbind[bigMatrix,x]
}

I guess it is because I can not rbind x and bigMatrix and assign it to bigMatrix itself?

What shall I do instead?

The processEachCSV functions is like this:

processEachCSV <- function (filename){

  x = read.table(filename, header=F, sep=',', fileEncoding='UTF-8')
  x$V4=as.numeric(gsub("[^0-9.]",'', as.character(x$V4)))
  x$V5=as.numeric(gsub("[^0-9.]",'', as.character(x$V5)))
  x$V6=substr(filename, 1, nchar(filename)-4)
  colnames(x)=c('DateTime','Site','AQI','PM25','PM10','City')
  x=as.matrix(x)
  return (x)
}

Answer 1

The basic approach would be something like:

do.call(rbind, lapply(filenames, read.csv))

Customize the read.csv part with whatever you actually do with your processEachCSV function (if that is indeed a function).

---

Alternatively, you can look at some of the rbind_list function from "dplyr" or the rbindlist function from "data.table", both of which are more efficient than do.call(rbind, ...) . The result would not be a matrix in those cases, but you can convert it to a matrix quite easily.